1. Technical Field
The present invention relates to a driving method and a driving apparatus of a liquid crystal display.
2. Discussion of Related Art
A liquid crystal display (LCOD) includes two panels provided with field generating electrodes, such as pixel electrodes and a common electrode, and a liquid crystal layer that has a dielectric anisotropy interposed therebetween. LCDs further include switching devices such as thin film transistors (TFTs) connected to the pixel electrodes and a plurality of signal lines such as gate lines and data lines to control the switching devices to apply voltages to the pixel electrodes. A common voltage is applied to the common electrode, which may be formed over the entire surface of one of two panels. The pixel electrodes, the common electrode, and the liquid crystal layer interposed therebetween together form liquid crystal capacitors.
A liquid crystal capacitor together with a switching element connected thereto forms a unit cell or “pixel”. An LCD includes a plurality of pixels arranged in a matrix.
An LCD generates an electric field in the liquid crystal layer by applying voltages to the field generating electrodes. The strength of the electric field is controlled to control transmittance of light that passes through the liquid crystal layer, thus obtaining desired images. To prevent degradation of the liquid crystal that can result when the electric field is applied for a long time in one direction to the liquid crystal layer, polarity of the data voltages with respect to the common voltage may be inverted by frames, by rows, or by pixels.
LCDs have been used as display devices for advertisement in outdoor environments.
Light that is reflected by an LCD screen increases as the illuminance (i.e., ambient light level) of the LCD increases, which may reduce the contrast ratio of an outdoor LCD and thereby image quality may be degraded.
The pupils of the human eye constrict as the illuminance increases, and a constricted pupil admits less light. Generally, when seeing a bright image, the human eye can only detect larger gray changes. Thus, on a bright day, a display function of the outdoor LCD may be reduced.